Method of making electric switches



Nov. 14, 1933. H, MASSEY 1,935,513

METHOD OF MAKING ELECTRIC SWI TCHES Filed Dec. 10, 1931 2 Sheets-Sheet lmm: I em NOV. 14, 1933. H MASSEY 1,935,513

METHOD OF' MAKING ELECTRIC SWITCHES Filed Dec. 10, 1931 2 Sheets-Sheet 2X I V/AIIIIIIIIW/ mm:

Patented Nov. 14, 1933 UNITED STATES PATENT OFFICE IL'ETHOD OF MAKINGELECTRIC SWITCHES Application December 10, 1931 Serial No. 580,140

3 Claims.

This invention relates to a method of making electric switches andparticularly to switches of the high contact pressure type whereincontact surfaces of very small area are provided by raised portionsformed on the switch members. More particularly, the invention relatesto a method of making the various members of a switch of this type, suchas is disclosed in applicants copending application Serial No. 551,456,filed July 1'7, 1931.

The principal object of the invention is'to provide a method of formingswitch members for switches of the above-stated type having polished andhard contact surfaces upstanding from the principal surfaces of therespective members, which method is simple and inexpensive to practiceand which produces highly efiicient contact surfaces which will notstick or burn under any conditions of service.

Other objects will appear from the following description andaccompanying drawings, where- Fig. 1 is a side elevational view showinga switch constructed according to the invention,

Figs. 2 and 3 are enlarged views showing the pivot terminal,

Figs. 4 and 5 are somewhat diagrammatic views showing the method offinishing the pivot terminal,

Figs. 6 and 7 are enlarged views showing the contact terminal,

Figs. 8 and 9 are somewhat diagrammatic views showing the method offinishing the contact terminal,

Fig. 10 is an enlarged view showing the blade,

and

Fig. 11 is a view showing the method of forming the contact buttons onthe blade.

One form of switch, constructed according to the present invention, isshown in its completed form in Fig. 1 and comprises three principalmembers, a pivot terminal 1, a pair of blades 2 pivoted thereto, and acontact terminal 3 disposed in the path of movement of the blades 2 forcooperation therewith. The blades 2 are pivoted to the pivot terminal 1by suitable means, such as a hollow rivet 4 which extends through aperforation 5 in the pivot terminal 1 and is spun over at its endsagainst spring washers 6, which washers 6 press the blades 2 againstraised annular ridges 7 formed on the pivot terminal 1. At the other endthe blades 2 are connected by a second hollow rivet 8 spun over againstspring washers 9, which rivet 8 and washers 9 resiliently limit theseparation of the blades 2 at their free ends. A notch 10 is formed inthe contact terminal 3 for the accommodation of the rivet 8, adjacentwhich slot 10 there are provided raised contact buttons 11 arranged tobear against alined raised contact bosses 12 projecting from theinwardly facing sides of the blades 2.

As described in the above referred to application, the annular ridges'7, the contact buttons 11, and the contact bosses 12 provide contactareas of the order of one one-hundredth of an inch. Since the totalpressure on these areas is,

for example, from 25 to 75 pounds, the unit pressure is very high. Ithas been found that where such high contact pressures are employed, thecurrent density that may be carried safely is also very high and hencelarge currents may cording to the present invention have such desirablecharacteristics of smoothness and hardness.

Referring to Figs. 2 and 3, the pivot terminal 1 is shown as comprising,a base portion 13 and an upstanding portion 14 through which theperforation 5 for accommodating the pivot rivet 4 extends. On each faceof the upstanding portion 14 and concentrically sin-rounding theperforation 5, are the raised annular ridges '7 which have asemicircular cross-section. A pair of perforations 15 are provided inthe base 13 to receive bolts (not shown) for securing conductors to theterminal and a second pair of perforations 16 are provided for bolts(not shown) by which the terminal end of a conductor (not shown) issecured to a supporting base 13.

The terminal 1 is cast from conducting ma-' terial, preferablyrelatively soft copper or copper alloys of high electrical and thermalconductivity,

with the ridges slightly thicker than the finished size. The terminal 1is then placed between a pair of dies 17, having annular grooves 18 intheir faces, which grooves 18 cooperate with the crest portion of therespective ridges 7. Pressure is applied to force the dies 1'! towardone another 1 to press the ridges '7 to the desired shape and size andto smooth and harden the crest portions thereof. It is not necessarythat the ridges be cast with the terminal and then die pressed asdescribed but they may be formed by any suitjoined to the terminal andhaving hard and smooth surfaces. The surfaces of the grooves 18 arehighly polished, and the curvature of the grooves 18 is preferablysomewhat fiatter than that of the cast ridges 7, thus insuring that theouter or contact portions of the ridges 7 will be most highlycompressed, polished and hardened. The bosses surrounding thebolt-receiving perforations in the base may be finished in a like mannerbut this is not generally practical since it is not necessary that thesurfaces of the bosses be of an exact size. The bosses are generallyfinished by a simple grinding operation.

It will be noted that the central perforation 5 for receiving the pivotrivet 1 is not drilled until after the die stamping operation. This isessential as'the lateral flow of metal in the diestamping step wouldtend to prevent the attainment of the desired hardness and polish at theridges 7.

In Figs. 6 and 7 is shown the contact terminal 3 which comprises, a baseportion 19 and an upstanding portion 20. In the upstanding portion 20 isformed the slot 10, thus providing a pair of arms 21 on which are formedthe dome-shaped contact buttons 11. Perforations 22, 23 for thereception of mounting bolts (not shown), and terminal bolts (not shown)are formed in the base 19 similar to the perforations 15, 16 in the base13 of the pivot terminal 1.

The contact terminal 3 is formed in a manner similar to that in whichthe pivot terminal 1 is formed, the terminal 3 being cast to the desiredsize and shape, except as to the contact buttons 11 which arei castslightly thicker than the desired thickness: The contact buttons 11 arepressed between dies 24 which cooperate with the crown portions of thebuttons 11 to force them into the proper size and shape. The press- 7ing also smooths and hardens the buttons 11 to provide satisfactorycontact surfaces.

The blade 2, shown in Fig. 10, is formed by cutting from a strip ofrolled conducting material,

preferably copper, a section of the desired length and pressing the samebetween a pair of male and female dies 25, 26 (as shown in Fig. 11) toforce out of the principal plane of the strip a pair of spacedbosses.12. After the bosses are formed, a perforation 27 is punched ordrilled, through the blade 2, intermediate the bosses 12 for thereception of the hollow rivet 8. A perforation 28 for the hollow pivotrivet 4 and a larger opening 29 adapted to receive a hook stick (notshown) for operating the switch are formed either before or after thebosses are pressed.

Where the blade 2 is formed of cast material instead of rolled material,raised contact buttons 1,985,513 =able process which will provide ridgesintimately are provided to replace the bosses and are finished in amanner similar to the manner in which the buttons 11 on the contactterminal 3 are finished.

From the above, it will be seen that the present invention provides asimple and inexpensive method for forming the various members of aswitch of the type herein described and that the contact surfaces soformed are smooth and hard, and thus will operate efficiently and willnot stick or burn under any conditions of service.

The copending application of Arthur T. Musgrave, Ser. No. 444,579, filedApril 15, 1930, describes and claims a method of forming hardenedcontact bosses on switch contact members by cold-working the metal ofthe member to project a hardened contact boss beyond the original planeof the member. In that process, the extreme surface of the boss which isto engage another switch contact member was not die pressed. Inaccordance with the present invention, the active surface of the raisedcontact boss, i. e., that portion which is to engage another contactmemher is hardened and smooth finished to the exact contour desired bycoin pressing in a die which is accurately shaped to that desiredcurvature.

I claim:

1. The method of forming pivot terminals for electric switches of thetype having axially alined contact rings which comprises, casting aterminal member having raised annular ridges formed on the side wallsand of approximately the desired shape and slightly excess thickness,applying a pressure on said ridges to harden and finish the surfaces ofthe crests of the ridges, and thereafter perforating the portion of theterminal member bounded by the ridges.

2. In the art of making electrical switch members of a copper-like metaland having contact surfaces projecting therefrom, the process whichcomprises shaping a mass of the copper-like metal to a blank havingoversized projecting surfaces thereon, and finishing the active portionsof said projecting surfaces to their final form by cold coin-pressingthe said oversized projecting surfaces, thereby simultaneously to hardenand smooth finish the same.

3. In the art of making an electrical contact member having contactsurfaces projecting beyond the body of the member, the process whichcomprises casting a mass of metal to form a homogeneous blank havingoversized contact surfaces projecting therefrom, and finishing theactive portions of said projecting surfaces to their final form by coldcoin-pressing the said oversized projecting surfaces, therebysimultaneously to harden and smooth finish the same.

HEMSLEY B.'MASSEY.

